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1.	Kokfelt, Ulla, et al. (författare) Wetland development, permafrost history and nutrient cycling inferred from late Holocene peat and lake sediment records in subarctic Sweden 2010 Ingår i: Journal of Paleolimnology. - : Springer Science and Business Media LLC. - 0921-2728 .- 1573-0417. ; 44:1, s. 327-342 Tidskriftsartikel (refereegranskat)abstract Permafrost in peatlands of subarctic Sweden is presently thawing at accelerated rates, which raises questions about the destiny of stored carbon and nutrients and impacts on adjacent freshwater ecosystems. In this study we use peat and lake sediment records from the Stordalen palsa mire in northern Sweden to address the late Holocene (5,000 cal BP-present) development of the mire as well as related changes in carbon and nutrient cycling. Formation, sediment accumulation and biogeochemistry of two studied lakes are suggested to be largely controlled by the development of the mire and its permafrost dynamics. Peat inception took place at ca. 4,700 cal BP as a result of terrestrialisation. Onset of organic sedimentation in the adjacent lakes occurred at ca. 3,400 and 2,650 cal BP in response to mire expansion and permafrost aggradation, respectively. Mire erosion, possibly due to permafrost decay, led to re-deposition of peat into one of the lakes after ca. 2,100 cal BP, and stimulated primary productivity in the other lake at ca. 1,900-1,800 cal BP. Carbonate precipitation appears to have been suppressed when acidic poor fen and bog (palsa) communities dominated the catchment mire, and permafrost-induced changes in hydrology may further have affected the inflow of alkaline water from the catchment. Elevated contents of biogenic silica and diatom pigments in lake sediments during periods of poor fen and bog expansion further indicate that terrestrial vegetation influenced the amount of nutrients entering the lake. Increased productivity in the lake likely caused bottom-water anoxia in the downstream lake and led to recycling of sediment phosphorous, bringing the lake into a state of self-sustained eutrophication during two centuries preceding the onset of twentieth century permafrost thaw. Our results give insight into nutrient and permafrost dynamics in a subarctic wetland and imply that continued permafrost decay and related vegetation changes towards minerotrophy may increase carbon and nutrient storage of mire deposits and reduce nutrient fluxes in runoff. Rapid permafrost degradation may on the other hand lead to widespread mire erosion and to relatively short periods of significantly increased nutrient loading in adjacent lakes.
2.	Adrielsson, Lena, et al. (författare) Den skuggande läroplanen : integrerad kommunikationsträning i den geologiska kandidatutbildningen 2014 Ingår i: Proceedings Utvecklingskonferens 13 – Att skriva för att leva, lära och lyckas. ; , s. 61-61 Konferensbidrag (övrigt vetenskapligt/konstnärligt)
3.	Andresen, Camilla Snowman, et al. (författare) Early Holocene terrestrial climatic variability along a North Atlantic Island transect: palaeoceanographic implications 2007 Ingår i: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791. ; 26:15-16, s. 1989-1998 Tidskriftsartikel (refereegranskat)abstract A synthesis of the early Holocene climatic development in the North Atlantic region is presented, based on three previously published lake records from southern Greenland (Lake N14), Iceland (Lake Torfadalsvatn) and the Faroe Islands (Lake Lykkjuvotn). The interval 11500-8500 cal BP has been divided into five phases with respect to the inferred strength of the North Atlantic Current (NAC) and Irminger Currents (IC). Phase 1 (11 500-10 750 cal BP) was characterised by the first establishment of the NAC and IC in the vicinity of the studied sites, interrupted by the Preboreal Oscillation around 11 200cal BP. Phase 2 (10 750-10 100 cal BP) was marked by a further warming step in southern Greenland rather concordant with a change into colder and more variable winters on the Faroe Islands. It is proposed that this could partly be related to a series of melt water outbursts disturbing the thermohaline circulation in the eastern Atlantic Ocean, resulting in a warming trend in the western region. During Phase 3 (10 100-9400cal BP) the strength of the IC reaching northwestern Iceland intensified. A more stable regime in surface circulation was established at the onset of Phase 4 (9400-8900 cal BP) in southern Greenland and was followed by a change towards further warm conditions on Iceland at the onset of Phase 5 (8900-8500 cal BP). (C) 2007 Elsevier Ltd. All rights reserved.
4.	Andresen, Camilla Snowman, et al. (författare) Rapid Holocene climate changes in the North Atlantic: evidence from lake sediments from the Faroe Islands 2006 Ingår i: Boreas. - : Wiley. - 1502-3885 .- 0300-9483. ; 35:1, s. 23-34 Tidskriftsartikel (refereegranskat)abstract Holocene records from two lakes on the Faroe Islands were investigated to determine regional climatic variability: the fairly wind-exposed Lake Starvatn on Streymoy and the more sheltered Lake Lykkjuvotn on Sandoy. Sediment cores were analysed for content of biogenic silica, organic carbon and clastic material, and magnetic susceptibility. In addition, a new qualitative proxy for past lake ice cover and wind activity was developed using the flux of clastic grains that are larger than 255 mu m. Both long-term and short-term climatic developments were similar between the two lakes, suggesting a response to a regional climate signal. The long-term climate development is characterized by early Holocene rapid warming followed by Holocene climatic optimum conditions ending around 8300 cal. yr BP. A more open landscape as evidenced from increased sand grain influx in the period 8300-7200 cal. yr BP could reflect the aftermath of the 8200 cal. yr BP event, although the event itself is not recognized in either of the two lake records. From around 7200 cal. yr BP the mid-Holocene climate deterioration is observed and from 4200 cal. yr BP the climate deteriorated further with increased amplitude of centennial cooling episodes.
5.	Björck, Svante, et al. (författare) Multi-proxy analyses of a peat bog on Isla de los Estados, easternmost Tierra del Fuego: a unique record of the variable Southern Hemisphere Westerlies since the last deglaciation 2012 Ingår i: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791. ; 42, s. 1-14 Tidskriftsartikel (refereegranskat)abstract We have analyzed an almost 14,000 year old peat sequence on the island of Isla de los Estados (55 degrees S. 64 degrees W), east of Tierra del Fuego, in the core of the Southern Hemisphere Westerlies. A multitude of methods have been used: high resolution C-14 dating; detailed lithologic descriptions including humification degree; loss on ignition; magnetic susceptibility; bulk density; pollen and spore analysis and determination of Aeolian sand influx. By combining proxies for wind and precipitation we have been able to reconstruct how the westerlies have varied over time in the Atlantic sector of the Southern Ocean. It shows that this westerly wind belt was most intense at the onset of the record, 13,600-13,200 cal BP, coinciding with the mid to late part of the Antarctic Cold Reversal, followed by a gradual decline. At 12,200 cal BP the westerlies seem to have shifted to a position south of Tierra del Fuego and this phase, the calmest and driest period on the island throughout the sequence, ended at 10,000 cal BP when the westerlies moved equatorward again. Since then the westerlies have been present but with a variable impact on the 55 degrees S latitude of the Atlantic. Mostly conditions have been fairly similar to today, but occasionally with a wider or narrower and/or weaker or stronger wind belt. At 7200 cal BP wind intensity began to increase and between 4500 and 3500 cal BP these southern latitudes experienced a distinct wind and precipitation maximum, both in terms of perseverance and intensity. Our results show a both wide and strong wind belt, with possible niveo-aeolian activity in Tierra del Fuego in winter, and possibly creating milder summers around the Antarctic Peninsula. In the later part of the Holocene, expansion contraction phases of the wind belt, especially in winter, seem to have been a common phenomenon. (C) 2012 Elsevier Ltd. All rights reserved.
6.	Edvardsson, Johannes, et al. (författare) Holocene peatland development and hydrological variability inferred from bog-pine dendrochronology and peat stratigraphy - a case study from southern Sweden 2012 Ingår i: Journal of Quaternary Science. - : Wiley. - 1099-1417 .- 0267-8179. ; 27:6, s. 553-563 Tidskriftsartikel (refereegranskat)abstract Dendrochronological analysis was applied to subfossil remains of Scots pine (Pinus sylvestris L.) buried in a South Swedish peat deposit. In combination with peat stratigraphy, this approach was explored for its potential to provide information on the local hydrological and depositional history at the site, forming the basis for a regional palaeohydrological analysis. A 726-year ring-width chronology was developed and assigned an absolute age of 7233-6508cal a BP (5284-4559 BC) through cross-dating with German bog-pine chronologies, whereas two short additional records of older ages were radiocarbon dated. Registration of growth positions of individual trees allowed assessment of the spatial dynamics of the pine population in response to hydrological changes and peatland ontogeny. Annually resolved growth variability patterns in the pine population reveal several establishment and degeneration phases, probably reflecting fluctuations in bog-surface wetness. A major establishment phase at 7200-6900?cal a BP reflects the onset of a period of lowered groundwater level, also indicated by increased peat humification, and a development consistent with regional temperature and lake level reconstructions revealed from other proxies. This study demonstrates that subfossil bog-pine populations may provide annually to decadally resolved reconstructions of local groundwater variability, which are highly relevant in a long-term palaeoclimatic context. Copyright (c) 2012 John Wiley & Sons, Ltd.
7.	Edvardsson, Johannes, et al. (författare) Late-Holocene expansion of a south Swedish peatland and its impact on marginal ecosystems: Evidence from dendrochronology, peat stratigraphy and palaeobotanical data 2014 Ingår i: The Holocene. - : SAGE Publications. - 0959-6836 .- 1477-0911. ; 24:4, s. 466-476 Tidskriftsartikel (refereegranskat)abstract In this study, a reconstruction of the long-term development and lateral expansion of a south Swedish peat bog was performed using a multi-proxy approach, including dendrochronology, peat stratigraphy and macrofossil and pollen analyses. By combining mapping of cross-dated subfossil trees with radiocarbon-dated peat sequences, an improved approach to reconstruction of lateral peat expansion was applied. Apart from providing approximate ages of tree burial episodes, the ring-width records offer information on hydrological variations prior to the bog expansion. New bog oak, pine and alder chronologies are presented and their potential as a dating tool for peatland expansion as well as for local to regional environmental interpretations is examined. Our tree-replication records show that increased amounts of bog trees in the central parts can be linked to drier bog-surface conditions, whereas an increase in wood remains in the marginal zone is related to enhanced preservation due to lateral bog expansion. Our reconstructions of the development of the peat deposit and associated changes in the distribution of vegetation communities provide new insight into peatland responses to climate change at the end of the 'Holocene Thermal Maximum' (5000-4000 cal. yr BP).
8.	Edvardsson, Johannes, et al. (författare) The Integrated Use of Dendrochronological Data and Paleoecological Records From Northwest European Peatlands and Lakes for Understanding Long-Term Ecological and Climatic Changes—A Review 2022 Ingår i: Frontiers in Ecology and Evolution. - : Frontiers Media SA. - 2296-701X. ; 10 Forskningsöversikt (refereegranskat)abstract Our overall understanding of long-term climate dynamics is largely based on proxy data generated from archives such as ice cores, ocean sediments, tree rings, speleothems, and corals, whereas reconstructions of long-term changes in vegetation and associated climate during the Holocene are largely based on paleoecological records from peat and lake sequences, primarily pollen and plant macrofossil data. However, since no proxy can provide a complete picture of the past, it is important to integrate different types of data, and to use methods that can support the paleoecological and paleoclimatic interpretations. Here we review how tree-ring data and dendrochronological approaches can be integrated with stratigraphic records to provide complementary paleoecological and paleoclimatic information. The review includes multiproxy studies in which dendrochronological data have been either compared or integrated with stratigraphic records, mainly pollen records, with the aim to contribute to a better understanding of long-term ecosystem and climate dynamics. We mainly focus on studies from northwest Europe in which tree-ring data and at least one type of paleoecological proxy record from the same site or area has been either compared or integrated. We find that integration of dendrochronological data and paleoecological records from peat and lake sequences is a powerful but underutilized approach to reconstruct long-term ecological and climatic changes. One likely reason for its limited use is the contrasting character of the two categories of data, including their different time resolution and occurrence, making them difficult to integrate. For example, subfossil wood providing annual dendrochronological data usually only occurs sporadically in peat and lake sediments, and the presence/absence of the trees are normally expected to be recorded in the pollen data with multi-decadal or coarser resolution. Therefore, we also discuss methods to compare and integrate dendrochronological and stratigraphic records, as well as the relevant paleoecological and paleoclimatic information provided by dendrochronology, pollen, and peat stratigraphy, with the aim to facilitate new multi-proxy initiatives that will contribute to a better understanding of long-term ecosystem and climate dynamics and thereby a firmer basis for future nature conservation initiatives.
9.	Eriksson Stenström, Kristina, et al. (författare) Environmental levels of radiocarbon in Lund, Sweden, prior to the start of the European Spallation Source 2022 Ingår i: Radiocarbon. - 0033-8222. ; 64:1, s. 51-56 Tidskriftsartikel (refereegranskat)abstract The European Spallation Source (ESS) is a neutron-based research facility under construction in Lund in southern Sweden. The spallation reactions will generate not only the desired neutrons, but also many radioactive byproducts, including 14C. As part of the licensing process, and as recommended by the IAEA, various preoperational studies are being carried out, including mapping the “zero-point” radiation environment around the site. As the city of Lund hosts several facilities using 14C-labeled substances, and since temporary and local 14C contamination have been observed in the past, 14C mapping is an important part of these baseline assessments. We here present a summary of 14C levels in various terrestrial environmental samples in Lund and in southern Sweden during the years 2012 to 2020. These environmental F14C do not display significantly elevated levels compared to sites located remote from Lund. We also describe a local 14C contamination event that was detected at the Lund Radiocarbon Dating Laboratory in 2009. Horse-chestnut leaves collected close to the laboratory exhibited F14C values of up to ∼25% above the clean air background. Elevated values of F14C were also found in a short tree-ring series, especially in 2007. The source of this contamination was identified and successfully removed.
10.	Fenhammar, Johan, et al. (författare) Renal effects of treatment with a TLR4-inhibitor in conscious septic sheep 2014 Ingår i: Critical Care. - : Springer Science and Business Media LLC. - 1364-8535 .- 1466-609X. ; 18:5, s. 488- Tidskriftsartikel (refereegranskat)abstract Introduction: Acute kidney injury (AKI) is a common and feared complication of sepsis. The pathogenesis of sepsis-induced AKI is largely unknown, and therapeutic interventions are mainly supportive. In the present study, we tested the hypothesis that pharmacological inhibition of Toll-like receptor 4 (TLR4) would improve renal function and reduce renal damage in experimental sepsis, even after AKI had already developed. Methods: Sheep were surgically instrumented and subjected to a 36-hour intravenous infusion of live Escherichia coli. After 12 hours, they were randomized to treatment with a selective TLR4 inhibitor (TAK-242) or vehicle. Results: The E. coli caused normotensive sepsis characterized by fever, increased cardiac index, hyperlactemia, oliguria, and decreased creatinine clearance. TAK-242 significantly improved creatinine clearance and urine output. The increase in N-acetyl-beta-D-glucosaminidas, a marker of tubular damage, was attenuated. Furthermore, TAK-242 reduced the renal neutrophil accumulation and glomerular endothelial swelling caused by sepsis. These effects were independent of changes in renal artery blood flow and renal microvascular perfusion in both cortex and medulla. TAK-242 had no effect per se on the measured parameters. Conclusions: These results show that treatment with a TLR4 inhibitor is able to reverse a manifest impairment in renal function caused by sepsis. In addition, the results provide evidence that the mechanism underlying the effect of TAK-242 on renal function does not involve improved macro-circulation or micro-circulation, enhanced renal oxygen delivery, or attenuation of tubular necrosis. TLR4-mediated inflammation resulting in glomerular endothelial swelling may be an important part of the pathogenesis underlying Gram-negative septic acute kidney injury.
11.	Fred, Mats, et al. (författare) Samverkan som marknadsskapande – introduktionen av social impact bonds i Sverige och Finland 2021 Ingår i: Perspektiv på samverkan : om utmaningar och möjligheter i välfärdens praktik - om utmaningar och möjligheter i välfärdens praktik. - 9789144143804 ; , s. 425-446 Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract Det är vanligt att anta att marknad och samverkan befinner sig i motsatsställning: på en marknad ska det idealt sett råda konkurrens mellan olika aktörer medan samverkan vanligen handlar om flera aktörers gemensamma strävan mot samma mål. Stater och inte minst EU:s institutioner vidtar regelbundet åtgärder för att skapa marknader och konkurrens, och i dessa åtgärder finns ofta direkta försök att förhindra samverkan mellan aktörer. I det här kapitlet undersöker vi en process där samverkan syftar till at skapa en ny marknad inom offentlig verksamhet - en marknad för social impact Bonds (SIB). Samverkan står i detta fall inte i motsättning till konkurrens eller marknad utan är snarare en strategi som aktörer använder sig av i marknadsskapande syfte.
12.	Fredh, Daniel, et al. (författare) Floristic diversity in the transition from traditional to modern land-use in southern Sweden AD 1800-2008 2012 Ingår i: Vegetation History and Archaeobotany. - : Springer Science and Business Media LLC. - 0939-6314 .- 1617-6278. ; 21:6, s. 439-452 Tidskriftsartikel (refereegranskat)abstract We aim to provide a long-term ecological analysis of land-use and floristic diversity in the transition from traditional to modern land-use management in the time a.d. 1800-2008 in southern Sweden. We use the Regional Estimates of Vegetation Abundance from Large Sites (REVEALS) model to quantify land-cover changes on a regional scale at 20-year intervals, based on the fossil pollen record. Floristic richness and evenness are estimated using palynological richness and the Shannon index applied to the REVEALS output, respectively. We identified a transition period of 60 years between 1880 and 1940 when the total tree cover increased and the tree composition changed from deciduous to coniferous dominance. Within the shrinking area of open land, arable land taxa expanded, while the number and coverage of herbs in the remaining grasslands decreased. The succession from open grasslands to more tree-covered habitats initially favoured palynological richness, which reached its highest values during the first 40 years of the transition period. The highest REVEALS-based evenness was recorded in the time of traditional land-use and at the beginning of the transition period, reflecting higher habitat diversity at these time intervals. Our results support a more dynamic ecosystem management that changes between traditional land-use and phases of succession (< 40 years) to promote floristic diversity. We have developed and applied a palaeoecological methodology that contributes realistic estimates to be used in ecosystem management.
13.	Fredh, Daniel, et al. (författare) The effect of local land-use changes on floristic diversity during the past 1000 years in southern Sweden 2017 Ingår i: Holocene. - : SAGE Publications. - 0959-6836. ; 27:5, s. 694-711 Tidskriftsartikel (refereegranskat)abstract The relationship between land-use and floristic diversity in the landscape, for the last millennia, is analysed from two small lakes in southern Sweden. Pollen analysis and the Local Vegetation Estimates (LOVE) model are used to quantify land-cover at local scales with 100-year time windows. Floristic richness is estimated using palynological richness, and we introduce LOVE-based evenness as a proxy for floristic evenness on a local scale based on the LOVE output. The results reveal a dynamic land-use pattern, with agricultural expansion during the 13th century, a partly abandoned landscape around AD 1400, re-establishment during the 15th–17th centuries and a transition from traditional to modern land-use during the 20th century. We suggest that the more heterogeneous landscape and the more dynamic land-use during the 13th–19th centuries were of substantial importance for achieving the high floristic diversity that characterises the traditional landscape. Pollen-based studies of this type are helpful in identifying landscape characteristics and land-use practices that are important for floristic diversity and may therefore guide the development of ecosystem management strategies aiming at mitigating the on-going loss of species seen in the landscape of southern Sweden and many other regions worldwide.
14.	Fredh, Daniel, et al. (författare) The impact of land-use change on floristic diversity at regional scale in southern Sweden 600 BC-AD 2008 2013 Ingår i: Biogeosciences. - : Copernicus GmbH. - 1726-4189. ; 10:5, s. 3159-3173 Tidskriftsartikel (refereegranskat)abstract This study explores the relationship between land-use and floristic diversity between 600 BC and AD 2008 in the uplands of southern Sweden. We use fossil pollen assemblages and the Regional Estimates of Vegetation Abundance from Large Sites (REVEALS) model to quantitatively reconstruct land cover at a regional scale. Floristic richness and evenness are estimated using palynological richness and REVEALS-based evenness, respectively. We focus on the period AD 350 to 750 to investigate the impact of an inferred, short-lived (< 200 yr) period of land-use expansion and subsequent land abandonment on vegetation composition and floristic diversity. The observed vegetation response is compared to that recorded during the transition from traditional to modern land-use management at the end of the 19th century. Our results suggest that agricultural land use was most widespread between AD 350 and 1850, which correlates broadly with high values of palynological richness. REVEALS-based evenness was highest between AD 500 and 1600 which indicates a more equal cover among taxa during this time interval. Palynological richness increased during the inferred land-use expansion after AD 350 and decreased during the subsequent regression AD 550-750, while REVEALS-based evenness increased throughout this period. The values of palynological richness during the last few decades are within the range observed during the last 1650 yr. However, REVEALS-based evenness shows much lower values during the last century compared to the previous ca. 2600 yr, which indicates that the composition of present-day vegetation is unusual in a millennial perspective. Our results show that regional scale changes in land use have had clear impacts on floristic diversity in southern Sweden, with a vegetation response time of less than 20 to 50 yr. We show the importance of traditional land use to attain high biodiversity and suggest that ecosystem management should include a regional landscape perspective.
15.	Gaillard, Marie-José, 1953-, et al. (författare) Holocene land-cover reconstructions for studies on land cover-climate feedbacks 2010 Ingår i: Climate of the Past. - : Copernicus GmbH. - 1814-9324 .- 1814-9332. ; 6, s. 483-499 Tidskriftsartikel (refereegranskat)abstract The major objectives of this paper are: (1) to review the pros and cons of the scenarios of past anthropogenic land cover change (ALCC) developed during the last ten years, (2) to discuss issues related to pollen-based reconstruction of the past land-cover and introduce a new method, REVEALS (Regional Estimates of VEgetation Abundance from Large Sites), to infer long-term records of past land-cover from pollen data, (3) to present a new project (LANDCLIM: LAND cover – CLIMate interactions in NW Europe during the Holocene) currently underway, and show preliminary results of REVEALS reconstructions of the regional land-cover in the Czech Republic for five selected time windows of the Holocene, and (4) to discuss the implications and future directions in climate and vegetation/land-cover modeling, and in the assessment of the effects of human-induced changes in land-cover on the regional climate through altered feedbacks. The existing ALCC scenarios show large discrepancies between them, and few cover time periods older than AD 800. When these scenarios are used to assess the impact of human land-use on climate, contrasting results are obtained. It emphasizes the need for methods such as the REVEALS model-based land-cover reconstructions. They might help to fine-tune descriptions of past land-cover and lead to a better understanding of how long-term changes in ALCC might have influenced climate. The REVEALS model is demonstrated to provide better estimates of the regional vegetation/landcover changes than the traditional use of pollen percentages. This will achieve a robust assessment of land cover at regional- to continental-spatial scale throughout the Holocene. We present maps of REVEALS estimates for the percentage cover of 10 plant functional types (PFTs) at 200 BP and 6000 BP, and of the two open-land PFTs “grassland” and “agricultural land” at five time-windows from 6000 BP to recent time. The LANDCLIM results are expected to provide crucial data to reassess ALCC estimates for a better understanding of the land suface-atmosphere interactions.
16.	Gaillard, Marie-José, 1953-, et al. (författare) Pollen-inferred quantitative reconstructions of Holocene land-cover in NW Europe for the evaluation of past climate-vegetation feedbacks : The Swedish LANDCLIM project and the NordForsk LANDCLIM network 2010 Konferensbidrag (refereegranskat)
17.	Geijer, Mats, 1957-, et al. (författare) Effective dose in low-dose CT compared with radiography for templating of total hip arthroplasty 2017 Ingår i: Acta Radiologica. - London, United Kingdom : Sage Publications. - 0284-1851 .- 1600-0455. ; 58:10, s. 1276-1282 Tidskriftsartikel (refereegranskat)abstract Background: Recently, total hip arthroplasty (THA) has come to focus on restoration of individual anatomy including femoral neck anteversion and global offset (femoral and acetabular offset). Three-dimensional (3D) computed tomography (CT) data could provide a better basis for preoperative templating. The use of CT has been hampered by high radiation dose.Purpose: To evaluate the effective dose used in pelvis and hip CT for THA templating.Material and Methods: CT data from two clinical trials of THA were evaluated for CT scan length and volume CT dose index (CTDIvol). The effective doses from hip-knee-ankle CT and pelvis and hip radiography were compared. Conversion factors for effective dose for radiography were calculated using the PCXMC software.Results: A reduced dose CT protocol for pelvis imaging gave a substantial dose reduction compared with standard CT, while maintaining sufficient image quality. Between the two clinical trials there was a significant reduction in effective CT dose corresponding to changes in the CT protocol (P<0.01). The CT dose for the latter group was similar to, but nevertheless significantly higher than for, radiography (P<0.01). However, in the latter group the theoretical minimum dose for CT, using the minimum scan length required by the templating software, was equal to the dose from radiography.Conclusion: Although the CT dose remained higher than for radiography, potential reductions in scan length could reduce the dose further so that CTwould have a comparable level of risk to radiography with the added benefit of 3D templating.
18.	Göransson, Viktoria (författare) Hyaluronan and Renal Fluid Handling : Studies during Normal and Pathological Conditions of Renal Function 2001 Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract The kidney is the major organ responsible for the regulation of the composition and volume of the body fluids, which is essential for homeostasis. The glycosaminoglycan hyaluronan (HA), with extreme water-binding capacity, is present in the interstitium of the kidney with a heterogenous distribution. The importance of HA in renal water-handling is unknown and was the focus of the present investigation.Acute water-loading in rats caused the amount of papillary HA to increase and during water deprivation, the amount was reduced. Gerbils, with extreme urine concentrating capacity, have less HA in the renal papilla in normal conditions and responded diametrically different to water-loading (reduction in HA). Renomedullary interstitial cells (RMICs), which are probably the main producers of HA in the renal medulla, were cultured at different media osmolalities to mimic the milieu of the medulla during variations in the water balance. The amount of HA found in the media was decreased at high osmolalities and increased at low osmolalities, thereby strengthening the in vivo results. CD44, an HA-receptor involved in the uptake and degradation of HA, was expressed on RMICs in an osmolality dependent manner. During high media osmolality, the CD44 expression increased and at lower osmolalities, the opposite occurred, probably due to the need for uptake and degradation of HA.Renal ischemia-reperfusion injury causes a cortical accumulation of HA, up-regulation of CD44, and a depression of functional parameters. The time periods of ischemia correlated with the accumulation of HA which, in turn, was inversely correlated to GFR. Hyaluronidase injections in this setting failed to reduce HA levels and significantly improve renal function.In conclusion, the results from the present study suggest an important role for HA and RMICs in renal water-handling and that the intrarenal distribution of HA is altered after ischemia-reperfusion injury, which correlates with renal dysfunction.
19.	Hannon, Gina E., et al. (författare) Dynamic early Holocene vegetation development on the Faroe Islands inferred from high-resolution plant macrofossil and pollen data 2010 Ingår i: Quaternary Research. - : Cambridge University Press (CUP). - 0033-5894 .- 1096-0287. ; 73:2, s. 163-172 Tidskriftsartikel (refereegranskat)abstract Vegetation dynamics during the earliest part of the Holocene (11,250-10,250 cal yr BP) have been reconstructed from a lacustrine sequence on Sandoy, the Faroe Islands, using detailed plant macrofossil and pollen evidence. The plant macrofossils suggest the initial vegetation was sparse herb and shrub tundra, with Salix herbacea and open-ground species, followed by the development of a denser and more species-rich arctic heathland after 11,150 cal yr BP. Despite high pollen values for Betula nana, macrofossils are rare. The bulk of the macrofossils recorded are S. herbacea and Empetrum leaves with numerous herb taxa and an abundance of Racomitrium moss. Conditions start to change around 10,800 cal yr BP, with increased catchment erosion and sediment delivery to the lake from ca. 10,600 cal yr BP, and a transition to alternating Cyperaceae and Poaceae communities between ca. 10,450 and 10,250 cal yr BP. This vegetation change, which has been recorded throughout the Faroes, has previously been interpreted as a retrogressive shift from woody shrubs to a herbaceous community. The detailed plant macrofossil data show the shift is the replacement of an Empetrum arctic heathland by grassland and moist sedge communities. These taxa dominate the modern landscape. (C) 2009 University of Washington. Published by Elsevier Inc. All rights reserved.
20.	Hansson, Anton, et al. (författare) A submerged Mesolithic lagoonal landscape in the Baltic Sea, south-eastern Sweden – Early Holocene environmental reconstruction and shore-level displacement based on a multiproxy approach 2018 Ingår i: Quaternary International. - : Elsevier BV. - 1873-4553 .- 1040-6182. ; 463, s. 110-123 Tidskriftsartikel (refereegranskat)
21.	Hansson, Anton, et al. (författare) Early Holocene Landscape Development and Baltic Sea History Based on High-Resolution Bathymetry and Lagoonal Sediments in the Hanö Bay, Southern Sweden 2017 Ingår i: Under the Sea: Archaeology and Palaeolandscapes of the Continental Shelf. - Cham : Springer International Publishing. - 2211-0577. - 9783319531601 ; 20, s. 197-209 Bokkapitel (refereegranskat)
22.	Hansson, Anton, et al. (författare) Shoreline displacement and human resource utilization in the southern Baltic Basin coastal zone during the early Holocene: New insights from a submerged Mesolithic landscape in south-eastern Sweden 2018 Ingår i: The Holocene. - : SAGE Publications. - 0959-6836 .- 1477-0911. ; 28:5, s. 721-737 Tidskriftsartikel (refereegranskat)abstract Along parts of the Hanö Bay coast in south-eastern Sweden, remains of a submerged landscape can be found down to depths of almost 25 m b.s.l. The coastal landscape was formed during two periods of lowered water levels in the Baltic Basin: the Yoldia Sea and the Initial Littorina Sea stages. In order to reconstruct the local environment and shoreline displacement during the Yoldia Sea and Ancylus Lake stages, sediment sequences were obtained at 4.5, 17.5 and 18.7 m b.s.l. Detailed bathymetric mapping was based on multi-beam echo-sounding while surveillance and sampling of tree remains and archaeological findings were performed through diving. The Yoldia Sea low-stand reached its minimum level at 24–25 m b.s.l. just before 10,800 cal. BP. During the subsequent Ancylus transgression, a slow-flowing river passed through the area, accumulating thick deposits of fine-grained organic sediments in lagoonal basins. The river was surrounded by open woodland dominated by pine. Based on successive flooding of rooted tree stumps, the transgression rate was estimated at 4 cm·yr−1, until the Ancylus high-stand was reached at 5 m b.s.l. at 10,400–10,300 cal. BP. Findings of worked aurochs and beaver bones provide evidence of human presence in the landscape and show the importance of terrestrial resources for their subsistence. These integrated palaeoecological and archaeological investigations demonstrate the importance of submerged landscapes with well-preserved sediment, wood and bone material for our understanding of southern Baltic coastal landscapes and their inhabitants during the Early Mesolithic.
23.	Hansson, Anton, et al. (författare) Shoreline Displacement, Coastal Environments and Human Subsistence in the Hanö Bay Region during The Mesolithic 2019 Ingår i: Quaternary. - : MDPI AG. - 2571-550X. ; 2:1 Tidskriftsartikel (refereegranskat)abstract Southern Scandinavia experienced significant environmental changes during the early Holocene. Shoreline displacement reconstructions and results from several zooarchaeological studies were used to describe the environmental changes and the associated human subsistence and settlement development in the Hanö Bay region of southern Sweden during the Mesolithic. GIS-based palaeogeographic reconstructions building on shoreline displacement records from eastern Skåne and western Blekinge together with a sediment sequence from an infilled coastal lake were used to describe the environmental changes during five key periods. The results show a rapid transformation of the coastal landscape during the Mesolithic. During this time, the investigated coastal settlements indicate a shift towards a more sedentary lifestyle and a subsistence focused on large-scale freshwater fishing. The development of permanent settlements coincided with an extended period of coastline stability and the development of rich coastal environments in a more closed forest vegetation. This study provides a regional synthesis of the shoreline displacement, coastal landscape dynamics and settlement development during the Mesolithic. It also demonstrates a new way of combining zooarchaeological and palaeoecological approaches, which can produce multi-faceted and highly resolved palaeoenvironmental reconstructions in a wide range of settings.
24.	Jessen, Catherine, et al. (författare) Abrupt climatic changes and an unstable transition into a late Holocene Thermal Decline: a multiproxy lacustrine record from southern Sweden 2005 Ingår i: Journal of Quaternary Science. - : Wiley. - 1099-1417 .- 0267-8179. ; 20:4, s. 349-362 Tidskriftsartikel (refereegranskat)abstract The transition from a middle Holocene relatively warm and stable climate to a cooler and unstable late Holocene climate is reconstructed using sediments from Lake Igelsjon, south-central Sweden. This multiproxy study illustrates local, regional and global scale responses to climatic change by focusing on a previously identified abrupt hydrological shift to cooler and/or wetter conditions around 4000 cal. yr BP. The results suggest that between ca. 4600 and ca. 3400 cal. yr BP, the environment around and within the lake responded in two major, well-defined steps: the first between 4450 and 4350 cal. yr BP and the second between 4000 and 3800 cal. yr BP. A series of rapid fluctuations of short duration were superimposed on the general cooling trend, with the most severe aquatic response peaking at ca. 3800 cal. yr BP. Pollen percentage and influx values show forest composition and pollen productivity changes and a distinct decline in total and Corylus pollen influx in the period of 4000-3500 cal. yr BP. Stomatal-based reconstruction of atmospheric CO2 concentration produced a tenuous decrease with a minimum between 3650 and 3500 cal. yr BP.
25.	Jessen, Catherine, et al. (författare) Climate forced atmospheric CO2 variability in the early Holocene: A stomatal frequency reconstruction 2007 Ingår i: Global and Planetary Change. - : Elsevier BV. - 1872-6364 .- 0921-8181. ; 57:3-4, s. 247-260 Tidskriftsartikel (refereegranskat)abstract The dynamic climate in the Northern Hemisphere during the early Holocene could be expected to have impacted on the global carbon cycle. Ice core studies however, show little variability in atmospheric CO2. Resolving any possible centennial to decadal CO2 changes is limited by gas diffusion through the firn layer during bubble enclosure. Here we apply the inverse relationship between stomatal index (measured on sub-fossil leaves) and atmospheric CO2 to complement ice core records between 11,230 and 10,330 cal. yr BP. High-resolution sampling and radiocarbon dating of lake sediments from the Faroe Islands reconstruct a distinct CO2 decrease centred on ca. 11,050 cal. yr BP, a consistent and steady decline between ca. 10,900 and 10,600 cal. yr BP and an increased instability after ca. 10,550 cal. yr BP. The earliest decline lasting ca. 150 yr is probably associated with the Preboreal Oscillation, an abrupt climatic cooling affecting much of the Northern Hemisphere a few hundred years after the end of the Younger Dryas. In the absence of known global climatic instability, the decline to ca. 10,600 cal. yr BP is possibly due to expanding vegetation in the Northern Hemisphere. The increasing instability in CO2 after 10,600 cal. yr BP occurs during a period of increasing cooling of surface waters in the North Atlantic and some increased variability in proxy climate indicators in the region. The reconstructed CO2 changes also show a distinct similarity to indicators of changing solar activity. This may suggest that at least the Northern Hemisphere was particularly sensitive to changes in solar activity during this time and that atmospheric CO2 concentrations fluctuated via rapid responses in climate. (c) 2006 Elsevier B.V. All rights reserved.
26.	Jessen, Catherine, et al. (författare) Variability and seasonality of North Atlantic climate during the early Holocene: evidence from Faroe Island lake sediments 2008 Ingår i: The Holocene. - : SAGE Publications. - 0959-6836 .- 1477-0911. ; 18:6, s. 851-860 Tidskriftsartikel (refereegranskat)abstract Based on their position in relation to major ocean currents, palaeoclimatic archives in the Faroe Islands are expected to be sensitive recorders of variations in North Atlantic circulation. The multiproxy analysis ( magnetic susceptibility, total carbon, nitrogen and sulphur, biogenic silica, grains > 255 mu m) of a lacustrine record with both winter and summer climate indicators illustrates the variability of Faroese climate during the early Holocene (c. 11 300-10 240 cal. yr BP) and allows comparison with other records in the region. Our high-resolution record suggests a period of predominantly winter cooling and increased storminess centred at c. 11 150 cal. yr BP followed by a period of stability between c. 11 000 and 10 680 cal. yr BP, which correlates with a time when the North Atlantic was particularly free of meltwater incursions. After c. 10 680 cal. yr BP, both winter and summer indicators show an increase in variability broadly synchronous with increased variability at other North Atlantic sites. Within this time period, a predominantly winter cooling centred at c. 10 600 cal. yr BP, a winter/summer cooling centred at c. 10 450 cal. yr BP and a winter/summer cooling centred at c. 10 300 cal. yr BP are recorded. These distinctive coolings correspond to periods of ice core delta O-18 inferred lowered atmospheric temperatures over Greenland and the reoccurrence of meltwater outbursts at c. 10 600, 10 500 and 10 350 cal. yr BP.
27.	Kaislahti Tillman, Päivi (författare) Holocene climate change in high latitudes recorded by stable isotopes in peat 2010 Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract A key to the understanding of natural and human induced climate variations is to reconstruct past changes from different environments. No outstanding method for general use has been pinpointed, instead, a need of multi-proxy studies is often stressed and the reconstructions are under constant improvement by new techniques. The aim of my PhD project is to test a relatively new method, stable carbon and oxygen isotopes isolated from single moss species, and develop climate reconstructions based on them. The main interest is to implement the method in records from northern peatlands where permafrost conditions prevail, and contribute to the discussion about the warming Arctic. The first part of the Licentiate thesis is a method study about the variation of stable carbon and oxygen isotope ratios in different moss plant components. Modern isotopic values were calibrated against instrumental climate records from the study region in west-central Canada. The impact of peat decay on proxies was investigated by colorimetric and chemical (C/N) methods. The results indicate that the isotope signal is well preserved in peat that started to accumulate c. 6000 years ago. Furthermore, statistical analyses imply that the variation of stable carbon isotope ratios in Sphagnum fuscum is significantly correlated to the variation of summer temperatures. A temperature reconstruction was developed in the second part of the thesis, based on stable carbon isotope ratios. Wet/dry periods were derived from the stable oxygen isotope record, macrofossil analysis, and the peat humification record. The results were compared with other proxy records from the vicinity of the study area. The main climate periods, such as The Mediaeval Warm Period and The Little Ice Age were registered in the temperature record. The amplitude of the temperature change was similar to especially those in chironomid based reconstructions, showing c. 6.5±1°C variation in July temperatures during the past 6.2 ka.
28.	Kokfelt, Ulla, et al. (författare) Ecosystem responses to increased precipitation and permafrost decay in subarctic Sweden inferred from peat and lake sediments 2009 Ingår i: Global Change Biology. - : Wiley. - 1354-1013 .- 1365-2486. ; 15:7, s. 1652-1663 Tidskriftsartikel (refereegranskat)abstract Recent accelerated decay of discontinuous permafrost at the Stordalen Mire in northern Sweden has been attributed to increased temperature and snow depth, and has caused expansion of wet minerotrophic areas leading to significant changes in carbon cycling in the mire. In order to track these changes through time and evaluate potential forcing mechanisms, this paper analyses a peat succession and a lake sediment sequence from within the mire, providing a record for the last 100 years, and compares these with monitored climate and active layer thickness data. The peat core was analysed for testate amoebae to reconstruct changes in peatland surface moisture conditions and water table fluctuations. The lake sediment core was analysed by near infrared spectroscopy to infer changes in the total organic carbon (TOC) concentration of the lake-water, and changes in δ13C and C, N and δ15N to track changes in the dissolved inorganic carbon (DIC) pool and the influence of diagenetic effects on sediment organic matter, respectively. Results showed that major shifts towards increased peat surface moisture and TOC concentration of the lake-water occurred around 1980, one to two decades earlier than a temperature driven increase in active layer thickness. Comparison with monitored temperature and precipitation from a nearby climate station indicates that this change in peat surface moisture is related to June–September (JJAS) precipitation and that the increase in lake-water TOC concentration reflects an increase in total annual precipitation. A significant depletion in 13C of sediment organic matter in the early 1980s probably reflects the effect of a single or a few consecutive years with anomalously high summer precipitation, resulting in elevated DIC content of the lake water, predominantly originating from increased export and subsequent respiration of organic carbon from the mire. Based on these results, it was not possible to link proxy data obtained on peat and lake-sediment records directly to permafrost decay. Instead our data indicate that increased precipitation and anomalously high rainfall during summers had a significant impact on the mire and the adjacent lake ecosystem. We therefore propose that effects of increased precipitation should be considered when evaluating potential forcing mechanisms of recent changes in carbon cycling in the subarctic.
29.	Loader, N J, et al. (författare) The role of inter-specific, micro-habitat and climatic factors on the carbon isotope (delta C-13) variability of a modern leaf assemblage from northern Scandinavia: implications for climate reconstruction 2006 Ingår i: Boreas. - : Wiley. - 1502-3885 .- 0300-9483. ; 35:2, s. 188-201 Tidskriftsartikel (refereegranskat)abstract To provide a basis for the interpretation of past climatic conditions from Quaternary leaf records, leaf carbon isotope (delta C-13) results are presented for 12 northern European dwarf-shrub, shrub and tree species growing across a network of 18 sites in northern Scandinavia. The role of micro-habitat (hummock/hollow) on carbon isotope trends is explored in addition to a comparison of the carbon isotope composition of both cellulose and wholeleaf material. The data are also examined against local meteorological variables (temperature, precipitation and vapour pressure deficit) at both species and genus levels. Results exhibit only modest coherence between selected plant species and low-order correlations with external climate forcings consistent with accepted models for carbon isotope fractionation. Potential for the analysis and interpretation of stable isotopic time series may still be identified; however, factors such as inter-plant variability, senescence, diagenesis and homogeneity need to be thoroughly addressed before such an approach may be used for palaeoenvironmental reconstructions. These findings highlight the complexities and limitations of spatial calibration methods.
30.	Loisel, Julie, et al. (författare) A database and synthesis of northern peatland soil properties and Holocene carbon and nitrogen accumulation 2014 Ingår i: The Holocene. - : SAGE Publications. - 0959-6836 .- 1477-0911. ; 24:9, s. 1028-1042 Tidskriftsartikel (refereegranskat)abstract Here, we present results from the most comprehensive compilation of Holocene peat soil properties with associated carbon and nitrogen accumulation rates for northern peatlands. Our database consists of 268 peat cores from 215 sites located north of 45 degrees N. It encompasses regions within which peat carbon data have only recently become available, such as the West Siberia Lowlands, the Hudson Bay Lowlands, Kamchatka in Far East Russia, and the Tibetan Plateau. For all northern peatlands, carbon content in organic matter was estimated at 42 +/- 3% (standard deviation) for Sphagnum peat, 51 +/- 2% for non-Sphagnum peat, and at 49 +/- 2% overall. Dry bulk density averaged 0.12 +/- 0.07 g/cm(3), organic matter bulk density averaged 0.11 +/- 0.05 g/cm(3), and total carbon content in peat averaged 47 +/- 6%. In general, large differences were found between Sphagnum and non-Sphagnum peat types in terms of peat properties. Time-weighted peat carbon accumulation rates averaged 23 +/- 2 (standard error of mean) g C/m(2)/yr during the Holocene on the basis of 151 peat cores from 127 sites, with the highest rates of carbon accumulation (25-28 g C/m(2)/yr) recorded during the early Holocene when the climate was warmer than the present. Furthermore, we estimate the northern peatland carbon and nitrogen pools at 436 and 10 gigatons, respectively. The database is publicly available at https://peatlands.lehigh.edu.
31.	Moen, Vibeke, et al. (författare) Feto-maternal osmotic balance at term. A prospective observational study 2018 Ingår i: Journal of Perinatal Medicine. - : WALTER DE GRUYTER GMBH. - 0300-5577 .- 1619-3997. ; 46:2, s. 183-189 Tidskriftsartikel (refereegranskat)abstract Objective: We performed the present study to investigate the feto-maternal osmotic relationship at term with the hypothesis that, in contrast to the literature, maternal plasma osmolality is lower than fetal levels. In a previous study, we found that maternal plasma sodium at delivery was consistently lower than the sodium in the umbilical artery. Our aim was to corroborate these results with analysis of osmolality. Methods: Blood was sampled from 30 women immediately before cesarean section and from the umbilical artery and vein before cord clamping and osmolality, sodium and albumin were analyzed. Results: Maternal osmolality was (mean; 95% confidence interval) 287.0 (285.8-288.2) mOsmkg/kg, arterial cord osmolality was 289.4 (287.9-291.0) mOsm/kg and venous cord osmolality was 287.3 (286.0-288.5) mOsm/kg. The paired difference between maternal and umbilical arterial osmolality was mean (SD) -2.4 (3.3) mOsm/kg (P amp;lt; 0.001), between maternal and umbilical vein -0.3 (3.0) mOsm/kg (P = 0.63) and between umbilical artery and vein -2.1 (2.8) mOsm/kg (P amp;lt; 0.001). Conclusion: Maternal osmolality was significantly lower than arterial cord osmolality confirming our previous results. The feto-maternal osmotic gradient favors water transport from the mother to the fetus and may increase the fetal risk of water intoxication when the mother ingests or is administered large volumes of electrolyte free solutions.
32.	Moen, Vibeke, et al. (författare) Hyponatraemia reversibly affects human myometrial contractility. An in vitro pilot study 2020 Ingår i: PLOS ONE. - : PUBLIC LIBRARY SCIENCE. - 1932-6203. ; 15:1 Tidskriftsartikel (refereegranskat)abstract Background In a previous study we found a significant correlation between dystocia and hyponatraemia that developed during labour. The present study examined a possible causal relationship. In vitro studies often use area under the curve (AUC) determined by frequency and force of contractions as a measure of myometrial contractility. However, a phase portrait plot of isometric contraction, obtained by plotting the first derivate of contraction against force of contraction, could indicate that bi-or multiphasic contractions might be less effective compared to the smooth contractions. Material and methods Myometrial biopsies were obtained from 17 women undergoing elective caesarean section at term. Each biopsy was divided into 8 strips and mounted isometrically in a force transducer. Seven biopsies were used in the first part of the study when half of the strips were immersed in the hyponatraemic study solution S containing Na+ 120 mmol/L and observed for 1 hour, followed by 1 hour in normonatraemic control solution C containing Na+ 136 mmol/L, then again in S for 1 hour, and finally 1 hour in C. The other half of the strips were studied in reverse order, C-S-C-S. The remaining ten biopsies were included in the second part of the study. Response to increasing doses of oxytocin (OT) in solutions S and C was studied. In the first part of the study we calculated AUC, and created phase portrait plots of two different contractions from the same strip, one smooth and one biphasic. In both parts of the study we registered frequency and force of contractions, and described appearance of the contractions. Results First part of the study: Mean (median) contractions per hour in C: 8.7 (7.6), in S 14,3 (13). Mean (SD) difference between groups 5.6 (4.2), p = 0.018. Force of contractions in C: 11.8 (10.2) mN, in S: 10.8 (9.2) mN, p = 0.09, AUC increased in S; p = 0.018. Bi-/multiphasic contractions increased from 8% in C to 18% in S, p = 0.001. All changes were reversible in C. Second part of the study: Frequency after OT 1.65 x 10-(9) M in C:3.4 (2.9), in S: 3.8 (3.2), difference between groups: p = 0.48. After OT 1.65 x 10-(7) M in C: 7.8 (8.9), increase from previous OT administration: p = 0.09, in S: 8.7 (9.0), p = 0.04, difference between groups, p = 0.32. Only at the highest dose of OT dose was there an increase in force of contraction in S, p = 0.05, difference between groups, p = 0.33. Initial response to OT was more frequently bi/multiphasic in S, reaching significance at the highest dose of OT(1.65 x 10-(7) M), p = 0.015. when almost all contractions were bi/multiphasic. Conclusion Hyponatraemia reversibly increased frequency of contractions and appearance of bi-or multiphasic contractions, that could reduce myometrial contractility. This could explain the correlation of hyponatraemia and instrumental delivery previously observed. Contractions in the hyponatraemic solution more frequently showed initial multiphasic contractions when OT was added in increasing doses. Longer lasting labours carry the risk both of hyponatraemia and OT administration, and their negative interaction could be significant. Further studies should address this possibility.
33.	Reuss, Nina, et al. (författare) Lake Ecosystem Responses to Holocene Climate Change at the Subarctic Tree-Line in Northern Sweden 2010 Ingår i: Ecosystems. - : Springer Science and Business Media LLC. - 1432-9840 .- 1435-0629. ; 13:3, s. 393-409 Tidskriftsartikel (refereegranskat)abstract A Holocene sediment sequence from Lake Seukokjaure, a subarctic lake at tree-line in northern Sweden, was analyzed to assess major changes in the structure and functioning of the aquatic ecosystem in response to climate change and tree-line dynamics. The compiled multi-proxy data, including sedimentary pigments, diatoms, chironomids, pollen, biogenic silica (BSi), carbon (C), nitrogen (N) elemental and stable-isotope records, and total lake-water organic carbon (TOC) concentration inferred from near-infrared spectroscopy (NIRS), suggest that the Holocene development of Lake Seukokjaure was closely coupled to changes in terrestrial vegetation with associated soil development of the catchment, input of allochthonous organic carbon, and changes in the light regime of the lake. A relatively productive state just after deglaciation around 9700 to 7800 cal years BP was followed by a slight long-term decrease in primary production. The onset of the local tree-line retreat around 3200 cal years BP was accompanied by more diverse and altered chironomid and diatom assemblages and indications of destabilized soils in the catchment by an increase in variability and absolute values of delta C-13. An abrupt drop in the C/N ratio around 1750 cal years BP was coupled to changes in the internal lake structure, in combination with changes in light and nutrient conditions, resulting in a shift in the phototrophic community from diatom dominance to increased influence of chlorophytes, likely dominated by an aquatic moss community. Thus, this study emphasizes the importance of indirect effects of climate change on tree-line lake ecosystems and complex interactions of in-lake processes during the Holocene.
34.	Rügheimer, Louise, 1970- (författare) Kidney Hyaluronan : Regulatory Aspects During Different States of Body Hydration, Nephrogenesis & Diabetes 2008 Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract The kidney regulates the excretion of water and electrolytes, which maintains homeostasis and enables control of arterial blood pressure. Hyaluronan, a large negatively charged interstitial glucosaminoglycan, is heterogeneously distributed within the kidney, primarily found in the medulla.Medullary hyaluronan content changes depending on the state of body hydration and plays a part in fluid regulation through its water binding and viscoelastic properties. The aim of this thesis was to provide new insight into the regulation of intrarenal hyaluronan during different states of body hydration, during completion of kidney development, and during diabetes mellitus.Dehydration reduces medullary interstitial hyaluronan in parallel with reduced hyaluronan synthase 2 gene expression and increased urinary hyaluronidase activity. Acute hydration results in an increase in medullary hyaluronan, an increase that requires nitric oxide and prostaglandins. Urinary hyaluronidase activity decreases during hydration. The elevation of hyaluronan is important for reducing water permeability of the interstitium i.e. favoring diuresis.Changes in hyaluronan concentration constitute a morphoregulatory pathway that plays a key role in nephrogenesis. The reduction in neonatal hyaluronan depended on an angiotensin II mediated process that does not appear dependent on lymph vessel formation. If angiotensin II is blocked with an ACE inhibitor, hyaluronan accumulates, which results in structural and functional abnormalities in the kidney. Renomedullary hyaluronan is elevated during uncontrolled diabetes, which coincides with induction of hyaluronan synthase 2 mRNA, hyperglycemia, glucosuria, proteinuria and overt diuresis. The levels of hyaluronan are probably at a terminus ad quem as no further response was seen during hydration. The higher interstitial expression of hyaluronan during diabetes may be involved in the progression of diabetic nephropathy.This thesis in physiology provides new mechanistic insights into the regulation of renal hyaluronan during various aspects of fluid handling.
35.	Rundgren, Mats (författare) Biostratigraphic Evidence of the Allerød-Younger Dryas-Preboreal Oscillation in Northern Iceland 1995 Ingår i: Quaternary Research. - : Cambridge University Press (CUP). - 0033-5894. ; 44:3, s. 405-416 Tidskriftsartikel (refereegranskat)abstract Basal sediments of Lake Torfadalsvatn, northern Iceland, record changes in terrestrial and limnic environments in the period 11,300-9000 14C yr B.P. These changes were probably forced by climate and connected with displacements of the marine polar front and sea-ice margin. Pollen, spores, green algae (Pediastrum), saturation isothermal remanent magnetization, and carbon content of the basal sediments provide the first detailed biostratigraphic record of the last glacial-interglacial transition in Iceland. During the first pioneer phase, beginning at ca. 11,300 14C yr B.P., grasses and fell-field herbs became established, and lake productivity was very low. At ca. 10,900 14C yr B.P., climatic and soil conditions became favorable for shrubs and dwarf shrubs. This change, together with increased limnic productivity, clearly indicates long seasons without ice-cover in the sea immediately north of Iceland. A return to a colder climate (Younger Dryas), probably in connection with a southward displacement of the marine polar front, occurred by 10,600 14C yr B.P. Shrub and dwarf-shrub vegetation disappeared, and limnic productivity diminished. A second pioneer vegetation phase, dominated by Oxyria/Rumex and grasses, was initiated by a change to longer seasons without sea ice at ca. 9900 14C yr B.P. This warming is also evident as a contemporaneous increase in lake productivity. After ca. 9400 14C yr B.P. the reestablishment of dwarf-shrub heaths and very high limnic productivity indicate further warming.
36.	Rundgren, Mats, et al. (författare) Century-scale changes of atmospheric CO2 during the last interglacial 2002 Ingår i: Geology. - 0091-7613. ; 30:2, s. 187-189 Tidskriftsartikel (refereegranskat)abstract The crucial role of atmospheric CO2 in glacial-interglacial transitions is demonstrated by recent ice-core studies that highlight the importance of accurate CO2 records for our understanding of Quaternary climate dynamics. Previous estimates of CO2 levels during the last interglacial stage (the Eemian) relied on measurements on air trapped in the Antarctic Vostok ice core. Due to uncertainties associated with in situ chemical alteration and gas diffusion, there is a need for independent estimates of past CO2 levels. Here we report 33 Eemian CO2 estimates based on the stomatal index of Salix herbacea L. leaves preserved in Greenland sediments. We reconstruct Eemian CO2 levels centered on 250-280 parts per million by volume (ppmv), in general agreement with ice-core data. Two deviating (lower) stomatal estimates may reflect diffusional smoothing of Vostok CO2, data and indicate century-scale Eemian CO2 variability.
37.	Rundgren, Mats, et al. (författare) Dynamic sea-level change during the last deglaciation of northern Iceland 1997 Ingår i: Boreas. - : Wiley. - 0300-9483 .- 1502-3885. ; 26:3, s. 201-215 Tidskriftsartikel (refereegranskat)abstract A detailed reconstruction of deglacial relative sea-level changes at the northern coast of Iceland, based on the litho- and biostratigraphy of lake basins, indicates an overall fall in relative sea level of about 45 m between 11 300 and 9100 BP, corresponding to an isostatic rebound of 77 m. The overall regression was interrupted by two minor transgressions during the late Younger Dryas and in early Preboreal, and these were probably caused by a combination of expansions of local ice caps and readvances of the Icelandic inland ice-sheet margin. Maximum absolute uplift rates are recorded during the regressional phase between the two transgressions (10 000-9850 BP), with a mean value of c. 15 cm ·14C yr-1 or 11-12 cm ·cal. yr-1. Mean absolute uplift during the regressional phase following the second transgression (9700-9100 BP) was around 6 cm ·14C yr-1, corresponding to c. 3 cm · cal. yr-1, and relative sea level dropped below present-day sea level at 9000 BP.
38.	Rundgren, Mats (författare) Early-holocene vegetation of northern Iceland : Pollen and plant macrofossil evidence from the Skagi peninsula 1998 Ingår i: Holocene. - : SAGE Publications. - 0959-6836. ; 8:5, s. 553-564 Tidskriftsartikel (refereegranskat)abstract Pollen and plant macrofossil records from two lakes on northernmost Skagi peninsula, northern Iceland, reflect a progressive closing of the vegetation cover during the early Holocene. This development was connected with the succession from an initial herb-tundra phase characterized by Oxyria digyna, Poaceae and Caryophyllaceae, through an intermediate dwarf-shrub phase dominated by Salix and Empetrum nigrum, to a shrub and dwarf-shrub phase with Juniperus communis, Betula nana, Salix and Poaceae. This development is similar to that recorded at other sites in northern Iceland, both with respect to the taxa involved and the timing of transitions between successional phases, which suggests that early-Holocene vegetational development in northern Iceland was forced by broad-scale climatic changes. The palaeobotanical data suggest a gradual early-Holocene warming in northern Iceland, which probably was connected with northward displacements of Atlantic waters and North Atlantic air masses. The deposition of the Saksunarvatn ash at 9000 BP caused a transitory phase of vegetational succession on northernmost Skagi.
39.	Rundgren, Mats, et al. (författare) Fossil leaves: Effective bioindicators of ancient CO2 levels? 2003 Ingår i: Geochemistry Geophysics Geosystems. - 1525-2027. ; 4 Tidskriftsartikel (refereegranskat)
40.	Rundgren, Mats, et al. (författare) Holocene wet shifts in NW European bogs : evidence for the roles of external forcing and internal feedback from a high-resolution study of peat properties, plant macrofossils and testate amoebae 2023 Ingår i: Journal of Quaternary Science. - : Wiley. - 0267-8179 .- 1099-1417. ; 38:3, s. 423-439 Tidskriftsartikel (refereegranskat)abstract Two conspicuous wet shifts in the peat stratigraphy of Store Mosse in southern Sweden, associated with bog-wide changes in vegetation and degree of peat decomposition, were analysed at high resolution. The bog-surface wetness (BSW) proxy data (organic matter bulk density, C/N ratio, plant macrofossils and testate amoebae) highlight the importance of interactions between vegetation composition, microtopography and degree of peat decomposition, and show that the bog system operated consistently during the two wet shifts (dated to c. 2700 and 1000 cal a bp) despite different internal and external conditions. A sensitive bog-system state, associated with a degraded microtopography and well-decomposed surface peat with low hydrological conductivity developed during sustained dry conditions, probably contributed to the large BSW amplitudes registered. Comparable bog systems are expected to operate in the same way, and regionally high sensitivity that developed in response to atmospheric circulation changes may partly explain synchronous registration of wet shifts. The wet shifts in Store Mosse were attributed to solar and volcanic forcing, respectively, and wet shifts of similar magnitude registered in other NW European bogs are likely to also have been externally forced.
41.	Rundgren, Mats, et al. (författare) Klimatet under kvartärtiden – vinglig resa, många förare 2007 Ingår i: Geologiskt Forum. - 1104-4721. ; 14:53, s. 10-15 Tidskriftsartikel (populärvet., debatt m.m.)
42.	Rundgren, Mats, et al. (författare) Last interglacial atmospheric CO2 changes from stomatal index data and their relation to climate variations 2005 Ingår i: Global and Planetary Change. - : Elsevier BV. - 1872-6364 .- 0921-8181. ; 49:1-2, s. 47-62 Tidskriftsartikel (refereegranskat)abstract A high-resolution atmospheric CO2 reconstruction based on stomatal index data obtained from Betula and Quercus leaf fragments extracted from the Danish Hollerup lake sediment section provides a unique insight into last interglacial CO2 dynamics. According to pollen stratigraphic correlations the CO2 record covers the first c. 7400 years of the Eemian, as palaeobotanically defined in northwestern Europe. The first c. 3000 years of the reconstruction are characterised by centennial to millennial CO2 variability in the interval 250-290 ppmv, while the remaining part of the record is generally more stable with slightly higher values (290-300 ppmv). According to pollen stratigraphic correlations this shift in CO2 dynamics is coincident with the end of the early Eemian climatic optimum in northwestern Europe. Pollen data from this region indicate that early Eemian CO2 instability may be linked to vegetation succession following deglaciation in Europe, but vegetation dynamics on other northern continents were probably also important. In addition, palaeoceanographic records from the Nordic seas indicate an influence of oceanic processes on the reconstructed Eemian CO2 evolution. A 300-year period of rapid CO2 oscillations immediately before the establishment of stable conditions is synchronous with a dry and cool event previously inferred from proxy data from the same sediment sequence, suggesting that this was a climatic event of regional or global significance. The presented CO2 reconstruction is in general agreement with previous ice core and stomatal-based CO2 data, although a larger variability compared with Vostok ice core data is evident. This may be explained partly by the different resolution of the two records and the inherent smoothing of ice core gas records.
43.	Rundgren, Mats, et al. (författare) Late-glacial and early Holocene variations in atmospheric CO2 concentration indicated by high-resolution stomatal index data 2003 Ingår i: Earth and Planetary Science Letters. - 1385-013X. ; 213:3-4, s. 191-204 Tidskriftsartikel (refereegranskat)abstract Data from ice cores suggest that Late-glacial and early Holocene atmospheric CO2 variations were rather conservative, the most important change being a gradual Younger Dryas increase. By contrast, palaeo-CO2 records based on the inverse relationship between CO2 Partial pressure and stomatal frequency of terrestrial plant leaves reflect a more dynamic CO2 evolution, including an abrupt decrease at the Allerod/Younger Dryas transition. Here we present a Late-glacial and early Holocene CO2 record based on stomatal index data from leaves preserved in the sediments of a small lake in southwestern Sweden. Three independent records constructed from stomatal index data of Salix polaris, Salix herbacea and Betula nana leaves were combined to form a high-resolution CO2 reconstruction for the period 12 800-10 800 cal yr BP. Atmospheric CO2 concentrations were found to have decreased rapidly from c. 260 ppmv to 210-215 ppmv within 200 years during the Allerod (GI-1)/Younger Dryas (GS-1) transition. After 100-200 years, CO2 concentration started to gradually increase to 270-290 ppmv at the end of the Younger Dryas stadial (GS-1). CO2 concentrations were relatively stable during the early Holocene, except for a short-lived period of lower (240-250 ppmv) values c. 11350-11200 cal yr BP. This Late-glacial and early Holocene CO2 evolution partly resembles previous stomatal-based CO2 reconstructions, and the overall trend is almost identical to that seen in ice-core records. The amplitude of change is, however, markedly higher in the Swedish stomatal-based record compared to the ice cores. This difference may partly be accounted for by the inherent smoothing of ice-core CO2 records caused by diffusion, but a major part of the difference in amplitude between ice-core and stomatal-based records still remains to be explained. Based on our reconstruction, atmospheric CO2 may have played an important role in climate dynamics during the last deglaciation. (C) 2003 Elsevier B.V. All rights reserved.
44.	Rundgren, Mats (författare) Late Weichselian and early Holocene changes of vegetation, climate and sea level on the Skagi peninsula, northern Iceland 1997 Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract Sediment sequences from five lakes on the Skagi peninsula, northern Iceland, were subjected to mineral magnetic analysis, carbon analysis, pollen analysis, plant macrofossil analysis, diatom analysis, radiocarbon dating and tephra analysis in order to make detailed reconstructions of vegetation, climate and sea level during the Late Weichselian and Early Holocene. The main purpose was to investigate if the dramatic deglacial climatic shifts recorded in proxy records from the North Atlantic region, such as ice cores, marine sediments and lake sediments, also are registered in Skagi lake sediments, which would be expected considering Iceland´s position in the middle of the North Atlantic Ocean, within the range of the Late Weichselian–Early Holocene migrations of the marine polar front. In addition, the project aimed at a better understanding of the environmental development on Iceland during the last deglaciation. The period 11,300-10,900 BP was found to be characterized by grass-tundra vegetation and low lake productivity, indicating cold climatic conditions. In addition, there was an overall fall in relative sea level. Milder conditions after 10,900 BP are reflected by an expansion of dwarf shrubs and increased limnic productivity, indicating long seasons without sea ice. Relative sea level continued to fall in the period 10,900-10,600 BP. An abrupt cooling at 10,600 BP caused a return to grass-tundra vegetation and low limnic productivity, and sea-ice conditions were probably heavy up to 9900 BP. A minor transgression occurred in the later part of this cold period. Abrupt warming at 9900 BP resulted in a change to herb-tundra vegetation and high lake productivity, indicating long seasons without sea ice. Relative sea level fell rapidly after 9900 BP, but turned into a minor transgression in the period 9800-9700 BP coincident with a short-lived cooling event. A dwarf-shrub expansion and raised limnic productivity at 9600 BP suggest milder conditions and absence of sea ice. Relative sea level fell below present sea level at 9000 BP. A rapid vegetation change at 8800 BP suggests a temperature rise and a change to drier summer conditions, and the vegetation in the period 8800-8000 BP may be described as a dwarf-shrub and shrub tundra. Another abrupt vegetational succession at 8000 BP, possibly indicating increased winter precipitation, resulted in dominant shrub and dwarf-shrub tundra vegetation in the period 8000-7800 BP. It was concluded that the Late Weichselian-Early Holocene development on Skagi fits well with palaeoclimatic data from other parts of the North Atlantic region, indicating a close connection between deglacial ocean circulation changes and climatic conditions on Iceland. The results further suggest that the polar front was located south of Iceland in the period 11,300-10,900 BP, that its position was north of Iceland in late Allerød (10,900-10,600 BP), and that the Preboreal oscillation (c. 9800-9700 BP) most likely was associated with a southward migration of the polar front. In addition, the recording of transgressions on Skagi during cold events (the Younger Dryas and the Preboreal oscillation) implies that the Icelandic lithosphere is extremely sensitive to changes in volume of glacial ice, which suggests low asthenosphere viscosities below Iceland.
45.	Rundgren, Mats, et al. (författare) Plant survival in Iceland during periods of glaciation? 1999 Ingår i: Journal of Biogeography. - : Wiley. - 0305-0270 .- 1365-2699. ; 26:2, s. 387-396 Tidskriftsartikel (refereegranskat)abstract Aim: The paper addresses the classical question of possible plant survival in Iceland during the last glacial period in the light of a palaeobotanical record from northern Iceland, spanning the period 11,300-9000 BP, including the Younger Dryas stadial. We review the Late Cenozoic fossil plant record, the past debate on glacial plant refugia in Iceland, and the evidence for ice-free areas during the Weichselian. Location: The investigated lake sediment record comes from Lake Torfadalsvatn, which is situated in the northwestern part of the Skagi peninsula in northern Iceland. Methods: The sediment chronology was constructed from the occurrence of the Vedde Ash and the Saksunarvatn ash, two well-dated Icelandic tephras, together with the results from five AMS and conventional radiocarbon dates performed on bulk sediment samples. The vegetational reconstruction was based on detailed pollen analysis of the sediment sequence. Results: The pollen analysis revealed that many of the taxa present in the area prior to the Younger Dryas stadial continued to produce pollen during that cold event. The more or less immediate reappearance of a few other pollen taxa at the Younger Dryas-Preboreal boundary suggests that these plants also survived, even if they did not produce sufficient pollen to be recorded during the Younger Dryas stadial. Main conclusions: We conclude that the relatively high plant diversity found in high Arctic areas and present-day nunataks in Iceland and Greenland, together with the fact that many plant species were able to survive the Younger Dryas stadial on the Skagi peninsula, suggest that species with high tolerance for climate fluctuations also survived the whole Weichselian in Iceland. This conclusion is supported by recent palaeoclimatic data from ice-cores and deep-sea sediments, indicating that Icelandic climate during the last glacial was only occasionally slightly colder than during the Younger Dryas stadial.
46.	Rundgren, Mats, et al. (författare) Stable carbon isotope composition of terrestrial leaves: inter- and intraspecies variability, cellulose and whole-leaf tissue difference, and potential for climate reconstruction 2003 Ingår i: Journal of Quaternary Science. - : Wiley. - 1099-1417 .- 0267-8179. ; 18:7, s. 583-590 Tidskriftsartikel (refereegranskat)abstract Stable carbon isotope analysis of terrestrial plant leaves preserved in Quaternary lake sediments has the potential to provide high-resolution reconstructions of past climatic conditions. Preferably, delta(13)C measurements should be made on a single leaf component, e.g. cellulose, but this approach is often precluded by limited leaf availability. Previous work suggests that reliable palaeoclimatic information also may be derived from delta(13)C measurements on whole-leaf tissue, given a similar degree of leaf decomposition between samples. Leaf delta(13)C data for 12 Scandinavian species of dwarf-shrubs, shrubs and trees, and a comparison of delta(13)C data on recent and late Holocene Salix herbacea leaves, revealed that the delta(13)C signal registered by holocellulose is largely reflected by measurements on whole-leaf tissue. Holocellulose was found to be consistently enriched in C-13, although this delta(13)C offset was smaller for subfossil leaves. This supports the use of delta(13)C measurements on whole-leaf tissue for climate reconstruction, at least for leaves preserved in soft, late Holocene sediments with minimal diagenetic effects. Leaf carbon and nitrogen data on fresh leaves of the same 12 Scandinavian species, and corresponding data on late Holocene Salix herbacea leaves, suggest that the leaf C:N ratio is a suitable indicator of the degree of leaf decomposition. Copyright (C) 2003 John Wiley Sons, Ltd.
47.	Rundgren, Mats (författare) Stratigraphy of peatlands in central and northern Sweden: evidence of Holocene climatic change and peat accumulation 2008 Ingår i: GFF. - 2000-0863. ; 130:Part 2, s. 95-107 Tidskriftsartikel (refereegranskat)abstract Early peat surveys demonstrated the potential to detect Holocene climatic changes in southern Sweden through analysis of the degree of decomposition of Sphagnum peat and motivated systematic collection of peat-strati graphic information during subsequent geological mappings in central and northern Sweden. The resulting (published and unpublished) data was compiled and reanalysed, taking into account unpublished radiocarbon data and developments in radiocarbon calibration and pollen-stratigraphic dating. Data from 61 carefully selected sites indicate a peat initiation maximum centred in the north 9500-8000 cal. BP and interpreted to primarily reflect climatic change. The cause for a secondary maximum 6000-5500 cal. BP centred further south is less clear. Peat deposition data show a continuous increase in the period 10 500-2000 cal. BP, with almost constant values during recent millennia, indicating that peatlands in the region acted as a long-term Holocene carbon sink and increasingly so until c. 2000 years ago. Sphagnum peat decomposition data display a long-term trend towards wetter conditions after 5000 cal. BP interpreted to primarily reflect progressively stronger westerly airflow and an accompanying increase in precipitation. These data also show that wet shifts occurred more frequently across the region around 3300, 2500-2100 and 1300 cal. BP. The timing of peak frequencies of wet shifts is similar to that of supposedly climate-related wet shifts identified in southern Sweden. Variability in frequency of wet shifts is most strongly pronounced in the south-west, with an apparent periodicity of 800-1000 years believed to reflect regular changes in westerly airflow during the mid and late Holocene.
48.	Skog, Göran, et al. (författare) Status of the Single Stage AMS machine at Lund University after 4 years of operation 2010 Ingår i: Nuclear Instruments & Methods In Physics Research Section B-Beam Interactions With Materials And Atoms. - : Elsevier BV. - 0168-583X. ; 268:7-8, s. 895-897 Konferensbidrag (refereegranskat)abstract The Lund SSAMS machine has been in routine operation since 2004. We present results from the last year of operation of the facility. The reference sample IAEA C7 and the "old" oxalic acid, Oxl, were used as secondary standards. As primary standard for calculations the OxII was used. The background and long term stability of the facility are discussed. We also report on the quality of the C-13/C-12 ratio from the SSAMS system. (C) 2009 Elsevier B.V. All rights reserved.
49.	Soehnlein, Oliver, et al. (författare) Anesthesia Aggravates Lung Damage and Precipitates Hypotension in Endotoxemic Sheep 2010 Ingår i: Shock. - 1540-0514. ; 34:4, s. 412-419 Tidskriftsartikel (refereegranskat)abstract Beneficial anti-inflammatory properties have been ascribed to volatile anesthetics in septic conditions, but no studies have compared anesthesia to the conscious state in a large-animal model. The aim of this study was to investigate the effect of isoflurane anesthesia on cardiovascular and respiratory function, leukocyte activation, and lung damage in a model of endotoxemia in sheep. Conscious (n = 6) and anesthetized (n = 6) sheep were made endotoxemic by continuous infusion of LPS for 48 h. Central hemodynamics were monitored continuously, and blood samples were collected regularly. Activation of leukocytes was assessed by surface expression of CD11b and plasma myeloperoxidase concentration. Lung damage was determined by electron microscopy, cell count in bronchoalveolar lavage fluid, and analysis of lung vascular permeability. Four additional animals (two conscious and two anesthetized) went through the same protocol but did not receive LPS. LPS infusion induced a hyperdynamic sepsis. The drop in total peripheral resistance was compensated by an increase in heart rate and cardiac output in the conscious group, whereas anesthetized sheep failed to compensate in this way. Endotoxemic isoflurane-anesthetized sheep also showed signs of aggravated lung edema formation and tissue damage together with enhanced neutrophil activation and lung tissue accumulation. Our data suggest that isoflurane in conjunction with mechanical ventilation blunts cardiovascular compensatory mechanisms in sepsis and enhances leukocyte activation, which may contribute to lung edema formation and tissue damage.
50.	Stridh, Sara, 1983- (författare) Regulation of Renal Hyaluronan in Water Handling : Studies in vivo and in vitro 2013 Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract Hyaluronan (HA) is a negatively charged extracellular matrix (ECM) component with water-attracting properties. It is the dominating ECM component in the renal medullary interstitium, where the amount changes in relation to hydration status: it increases during hydration and decreases during dehydration. It has, therefore, been suggested that HA participates in the regulation of renal fluid handling by changing the permeability properties of the interstitial space. This thesis investigates potential mechanisms for such a role in renal fluid regulation.The results demonstrate that the high renal HA content of late nephrogenesis decreases during the completion of kidney development in the rat, which takes place in the neonatal period. The heterogenous distribution of HA is mainly established during the first three weeks after birth. On day 21, the HA content is similar to that in the adult rat. The process is dependent on normal Ang II function. It primarily involves a reduction of HA synthase 2 expression and an increase of medullary hyaluronidase 1. The cortical accumulation of HA that results from neonatal ACE inhibition can partly explain the pathological condition of the adult kidney, which causes reduced urinary concentration ability and tubulointerstitial inflammation.It is possible to reduce renomedullary HA with the HA synthesis inhibitor 4-MU, and the kidney’s ability to respond to a hydration challenge will then be suppressed, without affecting GFR. The investigation of renomedullary interstitial cells (RMIC) in culture, shows that media osmolality and hormones of central importance for body fluid homeostasis, such as angiotensin II, ADH and endothelin, affect HA turnover through their effect on the RMICs, in a manner comparable to that found in vivo during changes in hydration status. In established streptozotocin-induced diabetes, HA is regionally accumulated in the kidney, proteinuria and polyuria, reduced urine osmolality, and reduced response to ADH V2 activation will occur. As opposed to the proteinuria, the HA accumulation is not sensitive to mTOR inhibition, suggesting an alternate pathway compared to other ECM components Taken together, the data suggest that during normal physiological conditions, renomedullary interstitial HA participates in renal fluid handling by affecting the interstitial prerequisites for fluid flux across the interstitial space. This is possible due to the water-attracting and physicochemical properties of this glycosaminoglycan. During pathological conditions, such as diabetes, the elevated interstitial HA can contribute to the defective kidney function, due to the proinflammatory and water-attracting properties of HA.

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